Dhcp issue

[Muhammad ALTAF]

We are currently experiencing an issue with our network setup that involves the DHCP server, Palo Alto firewall, core switch, and access switches.

Our DHCP server is connected to the Palo Alto firewall, followed by our core switch and access switches. The problem arises with VLAN-503, where the gateway is located in the firewall. However, in the core switch, there is no SVI configured for VLAN 503. As a result, clients are unable to obtain IP addresses within this setup.

Strangely, when we manually configure the SVI for VLAN 503 on the core switch, clients are then able to successfully receive IPs from the DHCP server.

Need support.

[Flavio Miranda · Accepted solution]

Hi @Muhammad ALTAF 

 The problem is probably related to DHCP relay. When you setup the SVI on the core, you are probably configuring the helper-address pointing to the DHCP server and the traffic is passing through the firewall via unicast. 

When you remove the SVI on the Core and move it to the firewall, the DHCP request is sent via broadcast from Core vlan to the Firewall.  Then, the firewall must have the "heper-address" on its interface. If the firewall does not support this feature, it will not work and you need to keep in on the core.

[M02@rt37]

Hello @Muhammad ALTAF,

On the vl503 Gateway on your Palo Alto, add dhcp relay pointing your DHCP Server IP address.